arc_take_screenshot

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden. It mentions taking a screenshot but does not disclose that the modes require user input (dragging region or clicking a window), nor does it explain what the tool returns (e.g., saved file path or raw data). This omission limits an AI agent's ability to anticipate the tool's behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely concise, consisting of a single sentence that efficiently conveys the core purpose and mode differentiation. It is front-loaded and contains no unnecessary words, making it easy for an AI agent to parse quickly.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given that the tool has only two parameters, no output schema, and requires user interaction (due to the modes), the description is incomplete. It fails to mention that the tool will prompt the user for input, what the output will be (e.g., saved file), or any side effects like taking focus. This leaves the agent with an incomplete understanding of the tool's full workflow.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3. The description adds minimal value beyond the schema: it restates the mode options and their meanings. While helpful for quick understanding, it does not provide additional semantic context such as default behavior or example values for save_path.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: taking a screenshot. It explicitly distinguishes between the two modes ('selection' for range selection, 'window' for window selection), which sets it apart from sibling tools that deal with page content or other actions.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description does not provide guidance on when to use this tool versus alternatives like arc_get_page_content or arc_get_page_images. It also does not mention prerequisites, such as the need for user interaction (clicking or dragging) or that it might block until the user completes the capture.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.